17  Unit 4: Earth-Sun Dynamics 5E

What factors have contributed to climate change in the past and are they contributing to climate change now?

HS-ESS2-4 Time: 5 Days

🌍 MYSTERY: Earth’s Climate Cycles 🌍

17.1 🔬 THE PHENOMENON

⚡ The amount of solar radiation hitting 65°N has been CYCLING UP AND DOWN for 750,000 years — repeating the same pattern every ~100,000 years! ⚡

17.1.1 🤔 THE BIG QUESTIONS:

• 🌀 Could natural cycles be causing today’s climate change?
• 🛸 How has Earth’s position in space changed over time?
• 🔥 What happens to Earth’s temperature when our orbit shifts?

18 Engage: Solar Radiation Patterns

18.1 Solar Radiation at 65°N

Connecting to our earlier questions about how Earth’s temperature has varied in the past, let’s analyze the total amount of energy from solar radiation reaching Earth at 65°N over the last 750,000 years.

Plot = require("@observablehq/plot")

// Extended Radiation Data (750k years)
radiationData = [
  {kya: 740, radiation: 460}, {kya: 720, radiation: 490},
  {kya: 700, radiation: 470}, {kya: 680, radiation: 440},
  {kya: 660, radiation: 500}, {kya: 640, radiation: 470},
  {kya: 620, radiation: 450}, {kya: 600, radiation: 480},
  {kya: 580, radiation: 510}, {kya: 560, radiation: 470},
  {kya: 540, radiation: 450}, {kya: 520, radiation: 490},
  {kya: 500, radiation: 460}, {kya: 480, radiation: 520},
  {kya: 460, radiation: 530}, {kya: 440, radiation: 480},
  {kya: 420, radiation: 460}, {kya: 400, radiation: 460}, 
  {kya: 380, radiation: 490}, {kya: 360, radiation: 470}, 
  {kya: 340, radiation: 440}, {kya: 320, radiation: 500}, 
  {kya: 300, radiation: 470}, {kya: 280, radiation: 450}, 
  {kya: 260, radiation: 480}, {kya: 240, radiation: 510}, 
  {kya: 220, radiation: 470}, {kya: 200, radiation: 450}, 
  {kya: 180, radiation: 490}, {kya: 160, radiation: 460}, 
  {kya: 140, radiation: 520}, {kya: 120, radiation: 530}, 
  {kya: 100, radiation: 480}, {kya: 80, radiation: 460}, 
  {kya: 60, radiation: 440}, {kya: 40, radiation: 470}, 
  {kya: 20, radiation: 450}, {kya: 0, radiation: 480}
]

// Vostok ice core data (kept for reference/comparison later)
iceCoreTempData = [
  {kya: 400, temp: -8}, {kya: 380, temp: -4}, {kya: 360, temp: -6},
  {kya: 340, temp: -8}, {kya: 320, temp: -3}, {kya: 300, temp: -6},
  {kya: 280, temp: -8}, {kya: 260, temp: -4}, {kya: 240, temp: -2},
  {kya: 220, temp: -6}, {kya: 200, temp: -8}, {kya: 180, temp: -4},
  {kya: 160, temp: -6}, {kya: 140, temp: -1}, {kya: 120, temp: 2},
  {kya: 100, temp: -4}, {kya: 80, temp: -6}, {kya: 60, temp: -8},
  {kya: 40, temp: -6}, {kya: 20, temp: -8}, {kya: 10, temp: -2},
  {kya: 0, temp: 0}
]

viewof timeRange = Inputs.range([0, 750], {
  step: 50,
  value: 750,
  label: "View last ___ thousand years:"
})

filteredRadData = radiationData.filter(d => d.kya <= timeRange)

Plot.plot({
  title: "Summer Radiation at 65°N Over the Past " + timeRange + ",000 Years",
  subtitle: "Solar Radiation (Watts/m²)",
  width: 750,
  height: 400,
  x: {label: "Thousands of Years Ago (kya)", reverse: true},
  y: {label: "Radiation (W/m²)", domain: [420, 550]},
  marks: [
    Plot.ruleY([480], {stroke: "#999", strokeDasharray: "4,4"}),
    Plot.areaY(filteredRadData, {x: "kya", y: "radiation", y2: 480, fill: d => d.radiation > 480 ? "#e74c3c" : "#3498db", fillOpacity: 0.4}),
    Plot.line(filteredRadData, {x: "kya", y: "radiation", stroke: "#2c3e50", strokeWidth: 2}),
    Plot.dot(filteredRadData.filter(d => d.radiation > 520), {x: "kya", y: "radiation", fill: "red", r: 5}),
    Plot.text(filteredRadData.filter(d => d.radiation > 520), {x: "kya", y: "radiation", text: d => "Peak", dy: -10, fontSize: 10})
  ]
})

18.1.1 🎯 DETECTIVE MODE: What Do You See?

1. 🔍 What repeating pattern jumps out at you in the last 750,000 years?
2. ⏰ How often does the radiation peak?
3. 🧊 Could this pattern explain Ice Ages?

🤯 WAIT — this pattern has been repeating for THREE-QUARTERS OF A MILLION YEARS?! Let’s find out WHY… 🤯

19 Explore: Earth’s Orbital Cycles

19.1 🎢 The THREE ORBITAL CYCLES

MISSION: Use these interactive models to gather evidence about Earth’s position in space. Could these orbital wobbles and stretches be causing the 100,000-year radiation pattern we just saw?

💡 DID YOU KNOW? In 1941, Serbian scientist Milutin Milankovitch figured out that Earth’s “wobbles” in space control Ice Ages. Mind = blown! 🤯

19.1.1 🔵 Cycle 1: ECCENTRICITY (~100,000 years)

THE STRETCH: Earth’s orbit changes from nearly circular ⭕ to more elliptical 🥚

viewof eccentricity = Inputs.range([0, 0.06], {
  step: 0.005,
  value: 0.017,
  label: "Eccentricity (current = 0.017):"
})

// Draw orbit with variable eccentricity
{
  const width = 500;
  const height = 400;
  const cx = width / 2;
  const cy = height / 2;
  const a = 180; // semi-major axis
  const b = a * Math.sqrt(1 - eccentricity * eccentricity); // semi-minor axis
  const c = a * eccentricity; // focal distance
  
  const svg = d3.create("svg")
    .attr("width", width)
    .attr("height", height);
  
  // Draw orbit ellipse
  svg.append("ellipse")
    .attr("cx", cx + c)
    .attr("cy", cy)
    .attr("rx", a)
    .attr("ry", b)
    .attr("fill", "none")
    .attr("stroke", "#3498db")
    .attr("stroke-width", 2);
  
  // Draw Sun at one focus
  svg.append("circle")
    .attr("cx", cx)
    .attr("cy", cy)
    .attr("r", 20)
    .attr("fill", "#f1c40f");
  
  svg.append("text")
    .attr("x", cx)
    .attr("y", cy + 5)
    .attr("text-anchor", "middle")
    .attr("font-size", "12px")
    .text("☀️");
  
  // Draw Earth positions
  svg.append("circle")
    .attr("cx", cx + c + a)
    .attr("cy", cy)
    .attr("r", 10)
    .attr("fill", "#3498db");
  
  svg.append("text")
    .attr("x", cx + c + a)
    .attr("y", cy - 20)
    .attr("text-anchor", "middle")
    .attr("font-size", "10px")
    .text("Aphelion (farthest)");
  
  svg.append("circle")
    .attr("cx", cx + c - a)
    .attr("cy", cy)
    .attr("r", 10)
    .attr("fill", "#2ecc71");
  
  svg.append("text")
    .attr("x", cx + c - a)
    .attr("y", cy - 20)
    .attr("text-anchor", "middle")
    .attr("font-size", "10px")
    .text("Perihelion (closest)");
  
  // Info box
  svg.append("rect")
    .attr("x", 10)
    .attr("y", 10)
    .attr("width", 200)
    .attr("height", 80)
    .attr("fill", "#f5f5f5")
    .attr("rx", 5);
  
  svg.append("text")
    .attr("x", 20)
    .attr("y", 35)
    .attr("font-size", "12px")
    .text(`Eccentricity: ${eccentricity.toFixed(3)}`);
  
  const distDiff = ((2 * a * eccentricity) / a * 100).toFixed(1);
  svg.append("text")
    .attr("x", 20)
    .attr("y", 55)
    .attr("font-size", "12px")
    .text(`Distance variation: ${distDiff}%`);
  
  svg.append("text")
    .attr("x", 20)
    .attr("y", 75)
    .attr("font-size", "11px")
    .attr("fill", "#666")
    .text(`Cycle: ~100,000 years`);
  
  return svg.node();
}

19.1.2 🌐 Cycle 2: OBLIQUITY (Axial Tilt) (~41,000 years)

THE WOBBLE: Earth doesn’t spin perfectly upright! Our axial tilt changes between 22.1° and 24.5° — affecting how extreme our seasons are! 🎿❄️🏖️

viewof tiltAngle = Inputs.range([22.1, 24.5], {
  step: 0.1,
  value: 23.5,
  label: "Axial Tilt (current = 23.5°):"
})

{
  const width = 500;
  const height = 350;
  
  const svg = d3.create("svg")
    .attr("width", width)
    .attr("height", height);
  
  // Draw orbital plane
  svg.append("line")
    .attr("x1", 50)
    .attr("y1", height/2)
    .attr("x2", width - 50)
    .attr("y2", height/2)
    .attr("stroke", "#ccc")
    .attr("stroke-width", 2)
    .attr("stroke-dasharray", "5,5");
  
  svg.append("text")
    .attr("x", width - 100)
    .attr("y", height/2 + 20)
    .attr("font-size", "11px")
    .attr("fill", "#999")
    .text("Orbital Plane");
  
  // Draw Earth
  const earthX = width / 2;
  const earthY = height / 2;
  const earthR = 60;
  
  svg.append("circle")
    .attr("cx", earthX)
    .attr("cy", earthY)
    .attr("r", earthR)
    .attr("fill", "#3498db");
  
  // Draw tilted axis
  const tiltRad = tiltAngle * Math.PI / 180;
  const axisLength = 120;
  
  svg.append("line")
    .attr("x1", earthX - axisLength * Math.sin(tiltRad))
    .attr("y1", earthY + axisLength * Math.cos(tiltRad))
    .attr("x2", earthX + axisLength * Math.sin(tiltRad))
    .attr("y2", earthY - axisLength * Math.cos(tiltRad))
    .attr("stroke", "#e74c3c")
    .attr("stroke-width", 3);
  
  // Angle indicator
  svg.append("text")
    .attr("x", earthX + 70)
    .attr("y", earthY - 80)
    .attr("font-size", "14px")
    .attr("font-weight", "bold")
    .attr("fill", "#e74c3c")
    .text(`${tiltAngle.toFixed(1)}°`);
  
  // Effect description
  const effect = tiltAngle > 23.5 ? "MORE extreme seasons" : tiltAngle < 23.5 ? "LESS extreme seasons" : "Current tilt";
  svg.append("rect")
    .attr("x", 20)
    .attr("y", 20)
    .attr("width", 180)
    .attr("height", 60)
    .attr("fill", "#f5f5f5")
    .attr("rx", 5);
  
  svg.append("text")
    .attr("x", 30)
    .attr("y", 45)
    .attr("font-size", "12px")
    .text(`Tilt: ${tiltAngle.toFixed(1)}°`);
  
  svg.append("text")
    .attr("x", 30)
    .attr("y", 65)
    .attr("font-size", "11px")
    .attr("fill", "#666")
    .text(effect);
  
  return svg.node();
}

19.1.3 🔄 Cycle 3: PRECESSION (~23,000 years)

THE SPIN: Earth’s axis wobbles like a spinning top 🌀 — changing which hemisphere points toward the Sun when we’re closest! This affects whether Northern or Southern summers are INTENSE.

viewof precessionAngle = Inputs.range([0, 360], {
  step: 15,
  value: 0,
  label: "Precession angle (degrees):"
})

{
  const width = 450;
  const height = 350;
  
  const svg = d3.create("svg")
    .attr("width", width)
    .attr("height", height);
  
  const cx = width / 2;
  const cy = height / 2;
  
  // Wobble circle (path of North Pole)
  svg.append("ellipse")
    .attr("cx", cx)
    .attr("cy", cy - 80)
    .attr("rx", 50)
    .attr("ry", 20)
    .attr("fill", "none")
    .attr("stroke", "#9b59b6")
    .attr("stroke-width", 2)
    .attr("stroke-dasharray", "5,5");
  
  // Earth
  svg.append("circle")
    .attr("cx", cx)
    .attr("cy", cy)
    .attr("r", 50)
    .attr("fill", "#3498db");
  
  // Wobbling axis
  const precRad = precessionAngle * Math.PI / 180;
  const wobbleX = 30 * Math.cos(precRad);
  const wobbleY = 15 * Math.sin(precRad);
  
  svg.append("line")
    .attr("x1", cx - wobbleX)
    .attr("y1", cy + 100 - wobbleY)
    .attr("x2", cx + wobbleX)
    .attr("y2", cy - 100 + wobbleY)
    .attr("stroke", "#e74c3c")
    .attr("stroke-width", 3);
  
  // North marker
  svg.append("circle")
    .attr("cx", cx + wobbleX)
    .attr("cy", cy - 100 + wobbleY)
    .attr("r", 8)
    .attr("fill", "#e74c3c");
  
  svg.append("text")
    .attr("x", cx + wobbleX + 15)
    .attr("y", cy - 100 + wobbleY)
    .attr("font-size", "12px")
    .text("N");
  
  // Info
  svg.append("rect")
    .attr("x", 10)
    .attr("y", height - 70)
    .attr("width", 200)
    .attr("height", 60)
    .attr("fill", "#f5f5f5")
    .attr("rx", 5);
  
  svg.append("text")
    .attr("x", 20)
    .attr("y", height - 45)
    .attr("font-size", "12px")
    .text(`Precession: ${precessionAngle}°`);
  
  svg.append("text")
    .attr("x", 20)
    .attr("y", height - 25)
    .attr("font-size", "11px")
    .attr("fill", "#666")
    .text("Cycle: ~23,000 years");
  
  return svg.node();
}

19.2 🔬 INVESTIGATION LAB: Crack the Climate Code! 🕵️

⚡ TIME TO BECOME AN ORBITAL DETECTIVE! ⚡

19.2.1 🎒 Materials:

• Graph paper or spreadsheet 📊
• Colored pencils 🎨
• Calculator 🧮
• Your detective skills 🔍

19.2.2 📋 Mission Steps:

STEP 1: Analyze the Cycles 🌀

1. Use the interactive simulations above to explore each cycle
2. Record observations in your data table:

Cycle	Period	Current Value	Range	Climate Effect
Eccentricity	~100,000 yrs	0.017	0.0 - 0.06	Changes total radiation received
Obliquity	~41,000 yrs	23.5°	22.1° - 24.5°	Changes seasonal contrast
Precession	~23,000 yrs	N/A	360° rotation	Changes timing of seasons

STEP 2: Connect to the Data 📈

Go back and review that radiation graph from the beginning!

1. 🎯 Which cycle’s period matches the big 100,000-year pattern?
2. 🌊 Could the other two cycles explain the smaller “wiggles”?

STEP 3: Make Your Claim 🎤

📣 YOUR VERDICT: Do Earth’s orbital cycles CAUSE those radiation changes? Back it up with EVIDENCE from the models and data!

20 Explain: Connecting Orbit to Climate

🧊 THE MILLION-DOLLAR QUESTION 🧊

Did Earth’s orbital wobbles ACTUALLY cause Ice Ages? 🤔

20.1 🌍 THE SECRET MECHANISM REVEALED

💥 PLOT TWIST: It’s not about total yearly radiation — it’s about SUMMER radiation at 65°N (high northern latitudes)!

20.1.1 Why 65°N Matters:

1. Most of Earth’s land mass is in the Northern Hemisphere
2. Ice sheets grow when summer is NOT warm enough to melt winter snow
3. When summer radiation at 65°N is LOW, ice sheets expand
4. When summer radiation at 65°N is HIGH, ice sheets retreat

20.1.2 The Feedback Loop:

Low summer radiation → Snow persists → Ice sheets grow → 
Higher albedo → More cooling → More ice growth

20.2 Comparing Radiation and Temperature

combinedData = iceCoreTempData.map(d => {
  const rad = radiationData.find(r => r.kya === d.kya);
  return {
    kya: d.kya,
    temp: d.temp,
    radiation: rad ? rad.radiation : 480
  };
})

Plot.plot({
  title: "Temperature vs. Summer Radiation at 65°N",
  width: 750,
  height: 400,
  x: {label: "Thousands of Years Ago", reverse: true},
  y: {label: "Temperature Anomaly (°C)", axis: "left"},
  marks: [
    Plot.line(combinedData, {x: "kya", y: "temp", stroke: "#e74c3c", strokeWidth: 2}),
    Plot.dot(combinedData.filter(d => d.temp > -2), {x: "kya", y: "temp", fill: "#e74c3c", r: 6}),
    Plot.text([{x: 350, y: 2}], {x: "x", y: "y", text: d => "Temperature", fill: "#e74c3c", fontSize: 12}),
    
    // Add radiation trend for comparison (scaled to fit)
    Plot.line(combinedData, {x: "kya", y: d => (d.radiation - 480) / 10 - 6, stroke: "#3498db", strokeWidth: 1, strokeDasharray: "4,2"}),
    Plot.text([{x: 350, y: -5}], {x: "x", y: "y", text: d => "Radiation (scaled)", fill: "#3498db", fontSize: 10})
  ]
})

20.2.1 💡 Key Ideas: Earth-Sun Dynamics

1. Temperatures on Earth have fluctuated greatly during human history, marked by glacial and interglacial periods
2. A pattern exists in the frequency of these fluctuations (~100,000 years)
3. The pattern is explained by cyclical changes in Earth’s orbit shape and tilt
4. These changes cause ice sheets to expand and retreat
5. Current orbital parameters suggest Earth should be cooling, yet global temperatures are increasing

21 Elaborate: Solar Activity vs. Glacial Cycles

☀️ BUT WAIT… WHAT ABOUT THE SUN? ☀️

21.1 🔥 Solar Activity Data

🤔 NEW THEORY ALERT: Some people say the Sun itself is getting brighter, causing climate change. We know orbital wobbles caused Ice Ages… but what about the Sun’s OUTPUT? Let’s investigate! 🕵️

solarData = [
  {year: 1880, tsi: 1365.5, temp: -0.16},
  {year: 1900, tsi: 1365.7, temp: -0.08},
  {year: 1920, tsi: 1365.6, temp: -0.25},
  {year: 1940, tsi: 1365.8, temp: 0.12},
  {year: 1960, tsi: 1365.9, temp: -0.01},
  {year: 1980, tsi: 1366.1, temp: 0.26},
  {year: 2000, tsi: 1366.0, temp: 0.42},
  {year: 2020, tsi: 1361.0, temp: 1.02}
]

Plot.plot({
  title: "Solar Output (TSI) vs Global Temperature",
  width: 700,
  height: 400,
  x: {label: "Year"},
  marks: [
    Plot.line(solarData, {x: "year", y: d => (d.tsi - 1360) * 2, stroke: "#f1c40f", strokeWidth: 2}),
    Plot.line(solarData, {x: "year", y: d => d.temp * 3 + 5, stroke: "#e74c3c", strokeWidth: 2}),
    Plot.text([{x: 1900, y: 12}], {x: "x", y: "y", text: d => "Solar Output", fill: "#f1c40f", fontSize: 12}),
    Plot.text([{x: 1900, y: 7}], {x: "x", y: "y", text: d => "Temperature", fill: "#e74c3c", fontSize: 12})
  ]
})

21.1.1 ✅ Analysis Questions

1. Has solar output increased significantly since 1980?
2. Has temperature increased significantly since 1980?
3. Can changes in solar output explain recent warming? Why or why not?

22 Evaluate: Are Orbital Factors Causing Warming Today?

🚨 THE FINAL VERDICT 🚨

So… are Earth’s orbital cycles causing climate change RIGHT NOW? 🌡️

22.1 📊 THE EVIDENCE SAYS…

Based on current orbital parameters:

Parameter	Current Value	Trend	Climate Effect
Eccentricity	0.017	Decreasing	Less seasonal variation
Obliquity	23.44°	Decreasing	Less extreme seasons
Precession	NH summer at aphelion	Changing slowly	Cooler NH summers

Conclusion: Based on Milankovitch cycles alone, Earth should be gradually cooling. The fact that Earth is warming despite this indicates another factor is at play.

This sets up our next investigation: What IS causing the warming?

---

22.2 🎮 CHALLENGE MODE: Test Your Knowledge! 🏆

🔥 Can you ace this quiz? Let’s find out! 🔥

quizData = [
  {
    question: "What is the approximate period of the eccentricity cycle?",
    options: ["23,000 years", "41,000 years", "100,000 years", "1 million years"],
    correct: 2,
    feedback: {
      correct: "🎉 YES! The eccentricity cycle takes about 100,000 years, which matches the major Ice Age pattern we saw in the data!",
      wrong: "❌ Not quite! Remember, the eccentricity cycle is the LONGEST of the three Milankovitch cycles. It takes about 100,000 years!"
    }
  },
  {
    question: "Why is summer radiation at 65°N latitude so important for ice ages?",
    options: [
      "It's where most people live",
      "It's where most land mass is located, and ice sheets need cool summers to persist",
      "The Sun is closest to Earth at this latitude",
      "Ocean currents are strongest here"
    ],
    correct: 1,
    feedback: {
      correct: "💯 PERFECT! Most land is in the Northern Hemisphere. When summers are cool at 65°N, snow doesn't melt and ice sheets GROW!",
      wrong: "❌ Think about it: Where is most of Earth's land? And what happens if summer isn't warm enough to melt winter snow?"
    }
  },
  {
    question: "Earth's current axial tilt is approximately:",
    options: ["22.1°", "23.5°", "24.5°", "45°"],
    correct: 1,
    feedback: {
      correct: "✅ Spot on! Earth currently tilts at 23.5° — right in the middle of its range!",
      wrong: "❌ Close! Earth's tilt right now is 23.5°, which is about halfway between the minimum (22.1°) and maximum (24.5°)."
    }
  },
  {
    question: "According to Milankovitch cycles, what should Earth's climate be doing right now?",
    options: ["Warming rapidly", "Staying constant", "Cooling gradually", "Experiencing an ice age"],
    correct: 2,
    feedback: {
      correct: "🧠 SMART! Based on orbital cycles alone, Earth should be cooling slightly. But it's warming instead — which means something ELSE is going on!",
      wrong: "❌ Actually, our orbital parameters suggest we should be cooling gradually. But we're warming instead... 🤔 Something else must be causing it!"
    }
  },
  {
    question: "What causes the ~100,000 year glacial-interglacial cycle?",
    options: [
      "Changes in the Sun's energy output",
      "Volcanic activity",
      "Changes in Earth's orbital eccentricity",
      "Human activity"
    ],
    correct: 2,
    feedback: {
      correct: "🌟 EXCELLENT! Eccentricity — the shape of Earth's orbit — drives the major 100,000-year cycle!",
      wrong: "❌ Nope! The 100,000-year cycle matches the eccentricity cycle — when Earth's orbit becomes more or less elliptical!"
    }
  },
  {
    question: "The precession cycle affects climate by:",
    options: [
      "Changing total solar radiation received",
      "Changing which season occurs at perihelion vs aphelion",
      "Changing Earth's distance from the Sun",
      "Changing the Sun's output"
    ],
    correct: 1,
    feedback: {
      correct: "🎯 NAILED IT! Precession changes WHEN (which season) Earth is closest to the Sun, making some hemispheres' summers more intense!",
      wrong: "❌ Think about what 'wobble' means — precession changes which SEASON happens when Earth is closest to or farthest from the Sun!"
    }
  },
  {
    question: "If Earth's axial tilt increased to 24.5°, seasons would become:",
    options: ["Less extreme", "More extreme", "Unchanged", "Reversed"],
    correct: 1,
    feedback: {
      correct: "💪 YES! Greater tilt = more extreme seasons. Summer gets HOTTER, winter gets COLDER!",
      wrong: "❌ Remember: Greater tilt means the Northern Hemisphere points MORE toward (or away from) the Sun, making seasons more extreme!"
    }
  },
  {
    question: "What is the significance of global warming occurring despite Milankovitch cycles predicting cooling?",
    options: [
      "Milankovitch cycles are wrong",
      "Another factor must be causing the warming",
      "The Sun's output has increased dramatically",
      "Earth's orbit has changed unexpectedly"
    ],
    correct: 1,
    feedback: {
      correct: "🔥 GENIUS! You got it! Orbital cycles say we should cool, but we're warming — so something NEW and POWERFUL must be at work!",
      wrong: "❌ The cycles aren't wrong — they've worked for hundreds of thousands of years! The fact that we're warming ANYWAY means a NEW factor is involved..."
    }
  }
]

viewof answer0 = Inputs.radio(quizData[0].options, {label: `❓ Question 1: ${quizData[0].question}`})
viewof answer1 = Inputs.radio(quizData[1].options, {label: `❓ Question 2: ${quizData[1].question}`})
viewof answer2 = Inputs.radio(quizData[2].options, {label: `❓ Question 3: ${quizData[2].question}`})
viewof answer3 = Inputs.radio(quizData[3].options, {label: `❓ Question 4: ${quizData[3].question}`})
viewof answer4 = Inputs.radio(quizData[4].options, {label: `❓ Question 5: ${quizData[4].question}`})
viewof answer5 = Inputs.radio(quizData[5].options, {label: `❓ Question 6: ${quizData[5].question}`})
viewof answer6 = Inputs.radio(quizData[6].options, {label: `❓ Question 7: ${quizData[6].question}`})
viewof answer7 = Inputs.radio(quizData[7].options, {label: `❓ Question 8: ${quizData[7].question}`})

mutable showResults = false

viewof submitButton = Inputs.button("🎯 Submit Answers & See Your Score!", {
  reduce: () => {
    mutable showResults = true;
    return Date.now();
  }
})

userAnswers = [answer0, answer1, answer2, answer3, answer4, answer5, answer6, answer7]

score = showResults ? userAnswers.reduce((sum, ans, i) => {
  const answerIndex = quizData[i].options.indexOf(ans);
  return sum + (answerIndex === quizData[i].correct ? 1 : 0);
}, 0) : null

percentage = score !== null ? Math.round((score / quizData.length) * 100) : null

showResults ? html`
<div>
  ${quizData.map((q, i) => {
    const userAnswer = userAnswers[i];
    const answerIndex = q.options.indexOf(userAnswer);
    const isCorrect = answerIndex === q.correct;
    const answered = userAnswer !== undefined;
    const bgColor = !answered ? "#f5f5f5" : isCorrect ? "#d4edda" : "#ffebee";
    const borderColor = !answered ? "#ccc" : isCorrect ? "#28a745" : "#dc3545";
    const icon = !answered ? "⚠️" : isCorrect ? "✅" : "❌";
    
    return html`
      <div style="background: ${bgColor}; border: 3px solid ${borderColor}; padding: 15px; margin: 15px 0; border-radius: 10px;">
        <strong>${icon} Question ${i + 1}:</strong> ${q.question}<br/>
        <strong>Your answer:</strong> ${answered ? userAnswer : "Not answered"}<br/>
        <strong>Correct answer:</strong> ${q.options[q.correct]}<br/>
        <div style="margin-top: 10px; font-style: italic; color: #333;">
          ${isCorrect ? q.feedback.correct : q.feedback.wrong}
        </div>
      </div>
    `;
  })}
  
  <div style="background: linear-gradient(135deg, ${percentage >= 80 ? '#43e97b' : percentage >= 60 ? '#feca57' : '#fa709a'} 0%, ${percentage >= 80 ? '#38f9d7' : percentage >= 60 ? '#ff6b6b' : '#fee140'} 100%); color: ${percentage >= 60 ? '#1a1a1a' : 'white'}; padding: 25px; margin: 25px 0; border-radius: 15px; text-align: center; box-shadow: 0 10px 30px rgba(0,0,0,0.3);">
    <div style="font-size: 2.5em; font-weight: 800; margin-bottom: 10px;">
      ${percentage >= 80 ? '🏆' : percentage >= 60 ? '👍' : '📚'}
    </div>
    <div style="font-size: 2em; font-weight: 700; margin-bottom: 15px;">
      Your Score: ${score}/${quizData.length} (${percentage}%)
    </div>
    <div style="font-size: 1.3em; font-weight: 600;">
      ${percentage >= 80 ? 
        "🌟 ORBITAL EXPERT! You've mastered Earth-Sun dynamics! You're ready to explain Ice Ages to anyone!" : 
        percentage >= 60 ? 
        "💪 SOLID WORK! You understand the basics. Review those tricky concepts and you'll be an expert!" : 
        "🔄 KEEP LEARNING! These concepts are tough. Go back through the chapter, play with the simulations, and try again!"}
    </div>
  </div>
</div>
` : html`<div style="text-align: center; padding: 20px; color: #666; font-style: italic;">
  📝 Answer all questions above, then click "Submit Answers" to see how you did!
</div>`

---